As the output current levels of power converters increases, interleaved topologies become widely used. A well-known topology is the interleaved buck converter (IBC), which presents as main characteristic a low ripple output current source behavior. Due to HID lamp voltage source characteristics and their acoustic resonance issue, it is necessary to drive them with nearly constant current with a square-wave shape. Therefore, a buck-interleaved converter can be advantageous for supplying high power HID lamps. The goal of this paper is a proposal of an electronic ballast based on a two-cell buck-interleaved converter for high power HID lamps, with current control loop, voltage sensing and constant power. A DC model based on averaged state-space technique is derived for the ballast, as well as an AC model based on small-signal disturbances. The results are verified experimentally and through simulation in Matlab/Simulink and PSIM softwares.